Issue: PHP deprecation warnings from league/csv were being output as HTML
(<br /><b>...) which broke JSON parsing in browser.
Fix: Set display_errors=0 in process-csv.php while keeping log_errors=1.
Errors still logged to error_log but not output to browser.
Reverted test-upload endpoint back to process-csv.php.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
